The improved font texture processing is a specialized DXT3 compressor written for SpriteFont that allows the font texture to be compressed but does not suffer any blocky artifacts usually associated with texture compression. Unfortunately you cannot just cherry-pick that one improvement.
We use FreeType to rasterize the font glyphs. It is usually a high quality rasterizer, but it also depends on the quality of the font being imported. I do not know how PhotoShop rasterizes its font glyphs, but its likely to be a complex, expensive and proprietary process.
Are you rendering the font at a scale of 1.0? The FreeType rasterizer may not be able to rasterize the fine detail in glyphs such as the lowercase 's', especially if the font does not include hinting for small point sizes.
There are better font rendering methods, such as signed distance field, but these require larger changes to work properly (specialized shaders, etc), that I would like to add support for, but these won't happen for a little while yet.